Security wise, I was wondering which services or programs I should disable --and how-- in a default Stella or/and CentOS install so as to remove any server capabilities in my children's computers!? The goal is to leave only workstation capabilities --say, like when one install Fedora workstation or Ubuntu for desktop.

Hi Nux.
I did a clean install of CentOS 7, with the minimal ISO.
When I first booted, there was not even a network running.
I was able to find the info somewhere on how to enable it, and I was then able to apply the instructions you've given above.
Ok, so on the next reboot, I'm still at at console prompt.
It doesn't seem there is a X server available.
Do you know which groupinstall to add to get a GUI now?

Well, I don't like the Gnome 3 and KDE desktop environments, and I wanted to have the least clutter possible on the hard disk.
It was a fun experience. (and I'm still using it)
However I use only the bottom panel and installed the mintmenu available on some repo. (Epel I think)